1. Field of the Invention
The present invention relates to an automatic leveling apparatus which automatically tilts the light axis of a headlamp in such a direction so as to offset a pitch angle that corresponds to an inclination of a vehicle in the longitudinal direction thereof. This operation will be hereinafter referred to as an "automatic leveling operation". In particular, the present invention is related to an automatic leveling apparatus for automatically controlling the alignment of the light axis of the headlamp in a vertical direction on the basis of a pitch angle obtained while the vehicle is stationary.
2. Description of the Related Art
A headlamp of this type is built so that, for example, a reflector equipped with a light source is supported on a lamp body so as to be tiltable about a horizontal axis, and the light axis of the reflector (headlamp) is tiltable about the horizontal axis by means of an actuator.
A conventional automatic leveling apparatus comprises pitch angle detection means and a vehicle speed sensor, both of which are mounted on a vehicle, and a control section for controlling operation of an actuator on the basis of detection signals output from the detection means and the sensor. The light axis of a headlamp (reflector) is controlled so as to constantly remain in a predetermined position relative to the road surface.
Automatic leveling comprises dynamic automatic leveling for constantly effecting an automatic leveling operation either while the vehicle is travelling or stationary, and static automatic leveling for effecting an automatic leveling operation while the vehicle is stationary.
The conventional automatic leveling apparatus is arranged so as to perform a leveling operation in real time in response to a change in the orientation of a vehicle stemming from acceleration and deceleration during travel and a change in the weight of the vehicle stemming from loading and unloading of cargo on or from the vehicle during halts, regardless of whether or not the vehicle is traveling or stationary. For this reason, the actuator is operated a very large number of times, thus consuming a large amount of power. Further, components constituting a drive mechanism, such as a motor and gears, are required to have great durability, thus adding to the overall cost of the apparatus.